Human Prekallikrein is a single-chain gamma globulin glycoprotein involved in contact activation, kinin formation, and the early stages of fibrinolysis[1].
References
[1] Wuepper KD, et al. Plasma prekallikrein: isolation, characterization, and mechanism of activation. J Exp Med. 1972 Jan;135(1):1-20. DOI:10.1084/jem.135.1.1